Using dispersed data structures to point to slice or date source replicas

ABSTRACT

A computing device includes an interface configured to interface and communicate with a dispersed storage network (DSN), a memory that stores operational instructions, and processing circuitry operably coupled to the interface and to the memory. The computing device obtains a data identifier associated with a data object and determines DSN address(es) associated with storage of one or more encoded data slice(s) (EDS(s)). The computing device selects slice names based on the DSN address(es) and issues at least a read threshold number of read slice requests using slice names to at least some storage units (SUs). When an insufficient number of EDSs is received, the computing device issues an alternate read slice request to an alternate SU. When a sufficient number of EDSs is received from the alternate SU and the computing device has received at least the read threshold number of EDSs, the computing device reconstructs the data segment.

CROSS REFERENCE TO RELATED PATENTS

The present U.S. Utility patent application claims priority pursuant to35 U. S.C. § 120, as a continuation-in-part (CIP) of U.S. Utility patentapplication Ser. No. 14/102,987, entitled “UPDATING SHARED GROUPINFORMATION IN A DISPERSED STORAGE NETWORK,” filed Dec. 11, 2013,pending, which claims priority pursuant to 35 U.S.C. § 119(e) to U.S.Provisional Application No. 61/760,962, entitled “MANAGING A DISPERSEDSTORAGE NETWORK POWER CONSUMPTION,” filed Feb. 5, 2013, both of whichare hereby incorporated herein by reference in their entirety and madepart of the present U.S. Utility patent application for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not applicable.

BACKGROUND OF THE INVENTION Technical Field of the Invention

This invention relates generally to computer networks and moreparticularly to dispersing error encoded data.

Description of Related Art

Computing devices are known to communicate data, process data, and/orstore data. Such computing devices range from wireless smart phones,laptops, tablets, personal computers (PC), work stations, and video gamedevices, to data centers that support millions of web searches, stocktrades, or on-line purchases every day. In general, a computing deviceincludes a central processing unit (CPU), a memory system, userinput/output interfaces, peripheral device interfaces, and aninterconnecting bus structure.

As is further known, a computer may effectively extend its CPU by using“cloud computing” to perform one or more computing functions (e.g., aservice, an application, an algorithm, an arithmetic logic function,etc.) on behalf of the computer. Further, for large services,applications, and/or functions, cloud computing may be performed bymultiple cloud computing resources in a distributed manner to improvethe response time for completion of the service, application, and/orfunction. For example, Hadoop is an open source software framework thatsupports distributed applications enabling application execution bythousands of computers.

In addition to cloud computing, a computer may use “cloud storage” aspart of its memory system. As is known, cloud storage enables a user,via its computer, to store files, applications, etc. on an Internetstorage system. The Internet storage system may include a RAID(redundant array of independent disks) system and/or a dispersed storagesystem that uses an error correction scheme to encode data for storage.

Prior art data storage systems may experience excessive communicationtraffic that makes retrieval of data from one or more components in suchprior art data storage systems very difficult in not impossible. In someinstance, such prior art data storage systems may be so adverselyaffected that data access simply fail to timeout without being serviced.There continues to exist room for improvement in the manner by whichdata storage systems operate.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a dispersed ordistributed storage network (DSN) in accordance with the presentinvention;

FIG. 2 is a schematic block diagram of an embodiment of a computing corein accordance with the present invention;

FIG. 3 is a schematic block diagram of an example of dispersed storageerror encoding of data in accordance with the present invention;

FIG. 4 is a schematic block diagram of a generic example of an errorencoding function in accordance with the present invention;

FIG. 5 is a schematic block diagram of a specific example of an errorencoding function in accordance with the present invention;

FIG. 6 is a schematic block diagram of an example of a slice name of anencoded data slice (EDS) in accordance with the present invention;

FIG. 7 is a schematic block diagram of an example of dispersed storageerror decoding of data in accordance with the present invention;

FIG. 8 is a schematic block diagram of a generic example of an errordecoding function in accordance with the present invention;

FIG. 9 is a schematic block diagram of another embodiment of adistributed computing system in accordance with the present invention;

FIG. 10 is a flowchart illustrating another example of providing dataaccess in accordance with the present invention; and

FIG. 11 is a diagram illustrating an embodiment of a method forexecution by one or more computing devices in accordance with thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of an embodiment of a dispersed, ordistributed, storage network (DSN) 10 that includes a plurality ofcomputing devices 12-16, a managing unit 18, an integrity processingunit 20, and a DSN memory 22. The components of the DSN 10 are coupledto a network 24, which may include one or more wireless and/or wirelined communication systems; one or more non-public intranet systemsand/or public internet systems; and/or one or more local area networks(LAN) and/or wide area networks (WAN).

The DSN memory 22 includes a plurality of storage units 36 that may belocated at geographically different sites (e.g., one in Chicago, one inMilwaukee, etc.), at a common site, or a combination thereof. Forexample, if the DSN memory 22 includes eight storage units 36, eachstorage unit is located at a different site. As another example, if theDSN memory 22 includes eight storage units 36, all eight storage unitsare located at the same site. As yet another example, if the DSN memory22 includes eight storage units 36, a first pair of storage units are ata first common site, a second pair of storage units are at a secondcommon site, a third pair of storage units are at a third common site,and a fourth pair of storage units are at a fourth common site. Notethat a DSN memory 22 may include more or less than eight storage units36. Further note that each storage unit 36 includes a computing core (asshown in FIG. 2, or components thereof) and a plurality of memorydevices for storing dispersed error encoded data.

Each of the computing devices 12-16, the managing unit 18, and theintegrity processing unit 20 include a computing core 26, which includesnetwork interfaces 30-33. Computing devices 12-16 may each be a portablecomputing device and/or a fixed computing device. A portable computingdevice may be a social networking device, a gaming device, a cell phone,a smart phone, a digital assistant, a digital music player, a digitalvideo player, a laptop computer, a handheld computer, a tablet, a videogame controller, and/or any other portable device that includes acomputing core. A fixed computing device may be a computer (PC), acomputer server, a cable set-top box, a satellite receiver, a televisionset, a printer, a fax machine, home entertainment equipment, a videogame console, and/or any type of home or office computing equipment.Note that each of the managing unit 18 and the integrity processing unit20 may be separate computing devices, may be a common computing device,and/or may be integrated into one or more of the computing devices 12-16and/or into one or more of the storage units 36.

Each interface 30, 32, and 33 includes software and hardware to supportone or more communication links via the network 24 indirectly and/ordirectly. For example, interface 30 supports a communication link (e.g.,wired, wireless, direct, via a LAN, via the network 24, etc.) betweencomputing devices 14 and 16. As another example, interface 32 supportscommunication links (e.g., a wired connection, a wireless connection, aLAN connection, and/or any other type of connection to/from the network24) between computing devices 12 & 16 and the DSN memory 22. As yetanother example, interface 33 supports a communication link for each ofthe managing unit 18 and the integrity processing unit 20 to the network24.

Computing devices 12 and 16 include a dispersed storage (DS) clientmodule 34, which enables the computing device to dispersed storage errorencode and decode data as subsequently described with reference to oneor more of FIGS. 3-8. In this example embodiment, computing device 16functions as a dispersed storage processing agent for computing device14. In this role, computing device 16 dispersed storage error encodesand decodes data on behalf of computing device 14. With the use ofdispersed storage error encoding and decoding, the DSN 10 is tolerant ofa significant number of storage unit failures (the number of failures isbased on parameters of the dispersed storage error encoding function)without loss of data and without the need for a redundant or backupcopies of the data. Further, the DSN 10 stores data for an indefiniteperiod of time without data loss and in a secure manner (e.g., thesystem is very resistant to unauthorized attempts at accessing thedata).

In operation, the managing unit 18 performs DS management services. Forexample, the managing unit 18 establishes distributed data storageparameters (e.g., vault creation, distributed storage parameters,security parameters, billing information, user profile information,etc.) for computing devices 12-14 individually or as part of a group ofuser devices. As a specific example, the managing unit 18 coordinatescreation of a vault (e.g., a virtual memory block associated with aportion of an overall namespace of the DSN) within the DSN memory 22 fora user device, a group of devices, or for public access and establishesper vault dispersed storage (DS) error encoding parameters for a vault.The managing unit 18 facilitates storage of DS error encoding parametersfor each vault by updating registry information of the DSN 10, where theregistry information may be stored in the DSN memory 22, a computingdevice 12-16, the managing unit 18, and/or the integrity processing unit20.

The DSN managing unit 18 creates and stores user profile information(e.g., an access control list (ACL)) in local memory and/or withinmemory of the DSN module 22. The user profile information includesauthentication information, permissions, and/or the security parameters.The security parameters may include encryption/decryption scheme, one ormore encryption keys, key generation scheme, and/or dataencoding/decoding scheme.

The DSN managing unit 18 creates billing information for a particularuser, a user group, a vault access, public vault access, etc. Forinstance, the DSN managing unit 18 tracks the number of times a useraccesses a non-public vault and/or public vaults, which can be used togenerate a per-access billing information. In another instance, the DSNmanaging unit 18 tracks the amount of data stored and/or retrieved by auser device and/or a user group, which can be used to generate aper-data-amount billing information.

As another example, the managing unit 18 performs network operations,network administration, and/or network maintenance. Network operationsincludes authenticating user data allocation requests (e.g., read and/orwrite requests), managing creation of vaults, establishingauthentication credentials for user devices, adding/deleting components(e.g., user devices, storage units, and/or computing devices with a DSclient module 34) to/from the DSN 10, and/or establishing authenticationcredentials for the storage units 36. Network administration includesmonitoring devices and/or units for failures, maintaining vaultinformation, determining device and/or unit activation status,determining device and/or unit loading, and/or determining any othersystem level operation that affects the performance level of the DSN 10.Network maintenance includes facilitating replacing, upgrading,repairing, and/or expanding a device and/or unit of the DSN 10.

The integrity processing unit 20 performs rebuilding of ‘bad’ or missingencoded data slices. At a high level, the integrity processing unit 20performs rebuilding by periodically attempting to retrieve/list encodeddata slices, and/or slice names of the encoded data slices, from the DSNmemory 22. For retrieved encoded slices, they are checked for errors dueto data corruption, outdated version, etc. If a slice includes an error,it is flagged as a ‘bad’ slice. For encoded data slices that were notreceived and/or not listed, they are flagged as missing slices. Badand/or missing slices are subsequently rebuilt using other retrievedencoded data slices that are deemed to be good slices to produce rebuiltslices. The rebuilt slices are stored in the DSN memory 22.

FIG. 2 is a schematic block diagram of an embodiment of a computing core26 that includes a processing module 50, a memory controller 52, mainmemory 54, a video graphics processing unit 55, an input/output (IO)controller 56, a peripheral component interconnect (PCI) interface 58,an IO interface module 60, at least one IO device interface module 62, aread only memory (ROM) basic input output system (BIOS) 64, and one ormore memory interface modules. The one or more memory interfacemodule(s) includes one or more of a universal serial bus (USB) interfacemodule 66, a host bus adapter (HBA) interface module 68, a networkinterface module 70, a flash interface module 72, a hard drive interfacemodule 74, and a DSN interface module 76.

The DSN interface module 76 functions to mimic a conventional operatingsystem (OS) file system interface (e.g., network file system (NFS),flash file system (FFS), disk file system (DFS), file transfer protocol(FTP), web-based distributed authoring and versioning (WebDAV), etc.)and/or a block memory interface (e.g., small computer system interface(SCSI), internet small computer system interface (iSCSI), etc.). The DSNinterface module 76 and/or the network interface module 70 may functionas one or more of the interface 30-33 of FIG. 1. Note that the IO deviceinterface module 62 and/or the memory interface modules 66-76 may becollectively or individually referred to as IO ports.

FIG. 3 is a schematic block diagram of an example of dispersed storageerror encoding of data. When a computing device 12 or 16 has data tostore it disperse storage error encodes the data in accordance with adispersed storage error encoding process based on dispersed storageerror encoding parameters. The dispersed storage error encodingparameters include an encoding function (e.g., information dispersalalgorithm, Reed-Solomon, Cauchy Reed-Solomon, systematic encoding,non-systematic encoding, on-line codes, etc.), a data segmentingprotocol (e.g., data segment size, fixed, variable, etc.), and per datasegment encoding values. The per data segment encoding values include atotal, or pillar width, number (T) of encoded data slices per encodingof a data segment i.e., in a set of encoded data slices); a decodethreshold number (D) of encoded data slices of a set of encoded dataslices that are needed to recover the data segment; a read thresholdnumber (R) of encoded data slices to indicate a number of encoded dataslices per set to be read from storage for decoding of the data segment;and/or a write threshold number (W) to indicate a number of encoded dataslices per set that must be accurately stored before the encoded datasegment is deemed to have been properly stored. The dispersed storageerror encoding parameters may further include slicing information (e.g.,the number of encoded data slices that will be created for each datasegment) and/or slice security information (e.g., per encoded data sliceencryption, compression, integrity checksum, etc.).

In the present example, Cauchy Reed-Solomon has been selected as theencoding function (a generic example is shown in FIG. 4 and a specificexample is shown in FIG. 5); the data segmenting protocol is to dividethe data object into fixed sized data segments; and the per data segmentencoding values include: a pillar width of 5, a decode threshold of 3, aread threshold of 4, and a write threshold of 4. In accordance with thedata segmenting protocol, the computing device 12 or 16 divides the data(e.g., a file (e.g., text, video, audio, etc.), a data object, or otherdata arrangement) into a plurality of fixed sized data segments (e.g., 1through Y of a fixed size in range of Kilo-bytes to Tera-bytes or more).The number of data segments created is dependent of the size of the dataand the data segmenting protocol.

The computing device 12 or 16 then disperse storage error encodes a datasegment using the selected encoding function (e.g., Cauchy Reed-Solomon)to produce a set of encoded data slices. FIG. 4 illustrates a genericCauchy Reed-Solomon encoding function, which includes an encoding matrix(EM), a data matrix (DM), and a coded matrix (CM). The size of theencoding matrix (EM) is dependent on the pillar width number (T) and thedecode threshold number (D) of selected per data segment encodingvalues. To produce the data matrix (DM), the data segment is dividedinto a plurality of data blocks and the data blocks are arranged into Dnumber of rows with Z data blocks per row. Note that Z is a function ofthe number of data blocks created from the data segment and the decodethreshold number (D). The coded matrix is produced by matrix multiplyingthe data matrix by the encoding matrix.

FIG. 5 illustrates a specific example of Cauchy Reed-Solomon encodingwith a pillar number (T) of five and decode threshold number of three.In this example, a first data segment is divided into twelve data blocks(D1-D12). The coded matrix includes five rows of coded data blocks,where the first row of X11-X14 corresponds to a first encoded data slice(EDS 1_1), the second row of X21-X24 corresponds to a second encodeddata slice (EDS 2_1), the third row of X31-X34 corresponds to a thirdencoded data slice (EDS 3_1), the fourth row of X41-X44 corresponds to afourth encoded data slice (EDS 4_1), and the fifth row of X51-X54corresponds to a fifth encoded data slice (EDS 5_1). Note that thesecond number of the EDS designation corresponds to the data segmentnumber.

Returning to the discussion of FIG. 3, the computing device also createsa slice name (SN) for each encoded data slice (EDS) in the set ofencoded data slices. A typical format for a slice name 60 is shown inFIG. 6. As shown, the slice name (SN) 60 includes a pillar number of theencoded data slice (e.g., one of 1-T), a data segment number (e.g., oneof 1-Y), a vault identifier (ID), a data object identifier (ID), and mayfurther include revision level information of the encoded data slices.The slice name functions as, at least part of, a DSN address for theencoded data slice for storage and retrieval from the DSN memory 22.

As a result of encoding, the computing device 12 or 16 produces aplurality of sets of encoded data slices, which are provided with theirrespective slice names to the storage units for storage. As shown, thefirst set of encoded data slices includes EDS 1_1 through EDS 5_1 andthe first set of slice names includes SN 1_1 through SN 5_1 and the lastset of encoded data slices includes EDS 1_Y through EDS 5_Y and the lastset of slice names includes SN 1_Y through SN 5_Y.

FIG. 7 is a schematic block diagram of an example of dispersed storageerror decoding of a data object that was dispersed storage error encodedand stored in the example of FIG. 4. In this example, the computingdevice 12 or 16 retrieves from the storage units at least the decodethreshold number of encoded data slices per data segment. As a specificexample, the computing device retrieves a read threshold number ofencoded data slices.

To recover a data segment from a decode threshold number of encoded dataslices, the computing device uses a decoding function as shown in FIG.8. As shown, the decoding function is essentially an inverse of theencoding function of FIG. 4. The coded matrix includes a decodethreshold number of rows (e.g., three in this example) and the decodingmatrix in an inversion of the encoding matrix that includes thecorresponding rows of the coded matrix. For example, if the coded matrixincludes rows 1, 2, and 4, the encoding matrix is reduced to rows 1, 2,and 4, and then inverted to produce the decoding matrix.

In some examples, note that dispersed or distributed storage network(DSN) memory includes one or more of a plurality of storage units (SUs)such as SUs 36 (e.g., that may alternatively be referred to adistributed storage and/or task network (DSTN) module that includes aplurality of distributed storage and/or task (DST) execution units 36that may be located at geographically different sites (e.g., one inChicago, one in Milwaukee, etc.). Each of the SUs (e.g., alternativelyreferred to as DST execution units in some examples) is operable tostore dispersed error encoded data and/or to execute, in a distributedmanner, one or more tasks on data. The tasks may be a simple function(e.g., a mathematical function, a logic function, an identify function,a find function, a search engine function, a replace function, etc.), acomplex function (e.g., compression, human and/or computer languagetranslation, text-to-voice conversion, voice-to-text conversion, etc.),multiple simple and/or complex functions, one or more algorithms, one ormore applications, etc.

FIG. 9 is a schematic block diagram of another embodiment of adistributed computing system in accordance with the present invention.This diagram includes a schematic block diagram of another embodiment ofa distributed computing system that includes a computing device 910, astorage unit (SU) (e.g., SU 1), an alternate SU (e.g., an alternate SU2), and another alternate SU (e.g., an alternate SU 3). Alternatively,the system may include any number of other alternate SUs. Each SU may beimplemented by one or more of a storage unit (SU), a storage server, adistributed computing server, a memory module, a memory device, a userdevice, a computing device, and a DS processing unit. The computingdevice 910 may be implemented utilizing one or more of a computingdevice, a SU, a SU, a storage server, a distributed computing server, auser device, a DS processing unit, the SU, the alternate SU, and theother alternate SU.

The system functions to provide access to slices stored in the SU andreplicated slices of the slices where the replicated slices are storedin one or more of the alternate SU and the other alternate SU. Thecomputing device 910 obtains a data identifier for data to be retrieved(e.g., receives the data identifier, performs a lookup). The computingdevice 910 accesses an index using the data identifier to identify oneor more dispersed or distributed storage network (DSN) addressesassociated with storage of one or more slices of the data. Such a DSNaddress may include one or more of a slice name, an alternate slicename, a source name, and an alternate source name. For example, a slicename and an alternate slice name are aliased to a common slice listed inthe index.

The computing device 910 selects a set of slice names based on the oneor more DSN addresses. The computing device 910 issues at least a readthreshold number of read slice requests using the selected set of slicenames to a set of SUs that includes at least one of the SU, thealternate SU, and/or the other alternate SU. The read slice requestsinclude a slice name of a desired slice for retrieval. The at least oneof the SU, the alternate SU, and/or the other alternate SU issues a readslice response to the computing device 910 where the read sliceresponses includes one or more of the slice name and the desired slice.When receiving a threshold number of slices (e.g., at least a decodethreshold number of slices for each data segment of a plurality of datasegments of the data), the computing device 910 decodes the receivesslices to reproduce the data. When not receiving the threshold number ofslices, the computing device 910 issues additional read slice requestsusing other slice names. For example, when the computing device 910 ismissing a slice from the SU, the computing device 910 issues analternate read slice request to the alternate SU to retrieve the slice.The alternate read slice request includes an alternate slice name forthe slice. The alternate SU issues and alternate read slice responsethat includes the slice when the alternate SU stores a replicated sliceof the slice.

The SU determines whether to provide one or more replicated slices for aslice stored in the SU (e.g., based on SU performance). For example, theSU determines to provide a replicated slice for the slice when the SU isoverloaded. When providing the one or more replicated slices, for eachslice, the SU generates an alternate slice name and issues a writereplicated slice request to an alternate SU where the request includesthe alternate slice name and the replicated slice. The replicated sliceis substantially the same as the slice. The write replicated slicerequest further includes one or more of the replicated slice, thealternate slice name, a storage time frame, and a performance threshold.For each slice, the SU updates the index to associate the alternateslice name with the data ID (e.g., multiple aliased slice names for thedata and/or for each data segment of the data).

The alternate SU receives an alternate read slice request for areplicated slice and issues an alternate read slice response to arequesting entity that includes a replicated slice when the replicatedslice is available to the alternate SU. Alternatively, or in additionto, in a similar fashion, the alternate SU may determine whether tofurther replicate a replicated slice to the other alternate SU.

In an example of operation and implementation, the computing device 910includes an interface configured to interface and communicate with adispersed or distributed storage network (DSN), a memory that storesoperational instructions, and a processing module, processor, and/orprocessing circuitry operably coupled to the interface and memory. Theprocessing module, processor, and/or processing circuitry is configuredto execute the operational instructions to perform various operations,functions, etc. In some examples, the processing module, processor,and/or processing circuitry, when operable within the computing devicebased on the operational instructions, is configured to perform variousoperations, functions, etc. in certain examples, the processing module,processor, and/or processing circuitry, when operable within thecomputing device is configured to perform one or more functions that mayinclude generation of one or more signals, processing of one or moresignals, receiving of one or more signals, transmission of one or moresignals, interpreting of one or more signals, etc. and/or any otheroperations as described herein and/or their equivalents.

In an example of operation and implementation, the computing device 910is configured to obtain a data identifier associated with a data object.In some examples, the data object is segmented into a plurality of datasegments, and a data segment of the plurality of data segments isdispersed error encoded in accordance with dispersed error encodingparameters to produce a plurality of encoded data slices (EDSs) that isdistributedly stored among a plurality of storage units (SUs) within theDSN. Also, note that a read threshold number of EDSs provides forreconstruction of the data segment. The computing device 910 is alsoconfigured to determine one of more DSN addresses associated withstorage of one or more of the plurality of EDSs and to select aplurality of slice names based on the one of more DSN addresses.

The computing device 910 is also configured to issue at least a readthreshold number of read slice requests using the plurality of slicenames to at least some of the plurality of SUs. When fewer than the readthreshold number of EDSs is received from the at least some of theplurality of SUs in response to issuance of the at least the readthreshold number of read slice requests, the computing device 910 isconfigured to issue an alternate read slice request to an alternate SUto retrieve an alternate EDS among the read threshold number of EDSs.Also, when the alternate EDS among the read threshold number of EDSs isreceived from the alternate SU and the computing device has received atleast the read threshold number of EDSs, the computing device 910 isconfigured to reconstruct the data segment.

In some examples, a DSN address of the one of more DSN addressesincludes a slice name of the plurality of slice names, an alternateslice name, a source name, and/or an alternate source name. Also, theslice name and the source name are aliased to a common slice listed inan index that associates the data identifier to the one of more DSNaddresses.

In certain other examples, when the at least the read threshold numberof EDSs is received from the at least some of the plurality of SUs inresponse to the issuance of the at least the read threshold number ofread slice requests, the computing device 910 is configured toreconstruct the data segment.

Note that a SU of the at least some of the plurality of SUs (e.g., SU 1)is configured to determine to provide one or more alternate EDSsincluding the alternate EDS to the alternate SU (e.g., alternate SU 2)to be stored temporarily in the alternate SU when the SU of the at leastsome of the plurality of SUs is overloaded based on servicing requestsfor at least one EDS stored within the SU of the at least some of theplurality of SUs. In some examples, note that the alternate EDS to bestored temporarily in the alternate SU is substantially same as an EDSstored within the SU of the at least some of the plurality of SUs.

Also, note that the SU of the at least some of the plurality of SUs visfurther configured to issue a write replicated slice request to thealternate SU (e.g., alternate SU 2). In some examples, note that thewrite replicated slice request includes an alternate slice name, areplicated EDS, a storage time frame, and/or a performance threshold.

In some examples, with respect to a data object, the data object issegmented into a plurality of data segments, and a data segment of theplurality of data segments is dispersed error encoded in accordance withdispersed error encoding parameters to produce a set of encoded dataslices (EDSs) that are distributedly stored in a plurality of storageunits (SUs) within the DSN. In some examples, the set of EDSs is ofpillar width. Also, with respect to certain implementations, note thatthe decode threshold number of EDSs are needed to recover the datasegment, and a read threshold number of EDSs provides for reconstructionof the data segment. Also, a write threshold number of EDSs provides fora successful transfer of the set of EDSs from a first at least onelocation in the DSN to a second at least one location in the DSN. Theset of EDSs is of pillar width and includes a pillar number of EDSs.Also, in some examples, each of the decode threshold, the readthreshold, and the write threshold is less than the pillar number. Also,in some particular examples, the write threshold number is greater thanor equal to the read threshold number that is greater than or equal tothe decode threshold number.

Note that the computing device as described herein may be located at afirst premises that is remotely located from a second premisesassociated with at least one other computing device, SU, DS unit, atleast one SU of a plurality of SUs within the DSN (e.g., such as aplurality of SUs that are implemented to store distributedly the set ofEDSs), etc. In addition, note that such a computing device as describedherein may be implemented as any of a number of different devicesincluding a managing unit that is remotely located from anothercomputing device, SU, DS unit, etc. within the DSN and/or other devicewithin the DSN, an integrity processing unit that is remotely locatedfrom another computing device and/or other device within the DSN, ascheduling unit that is remotely located from another computing deviceand/or SU within the DSN, and/or other device. Also, note that suchcomputing device as described herein may be of any of a variety of typesof devices as described herein and/or their equivalents including a DSunit and/or SU included within any group and/or set of DS units and/orSUs within the DSN, a wireless smart phone, a laptop, a tablet, apersonal computers (PC), a work station, and/or a video game device.Also, note also that the DSN may be implemented to include or be basedon any of a number of different types of communication systems includinga wireless communication system, a wire lined communication system, anon-public intranet system, a public internet system, a local areanetwork (LAN), and/or a wide area network (WAN).

FIG. 10 is a flowchart illustrating another example of providing dataaccess in accordance with the present invention. This diagram includes aflowchart illustrating another example of providing data access. Themethod 1000 begins at a step 1010 where a storage unit (SU) determinesto provide one or more replicated slices for a slice stored in the SU(e.g., based on one or more of a SU performance level and a performancethreshold level). For each slice of the one or more replicated slices,the method 1000 continues at the step 1012 where the SU generates analternate slice name. The generating may be based on one or more of avault ID, a slice name of the slice, a data identifier associated withthe slice, and an offset scheme. For each slice of the one or morereplicated slices, the method 1000 continues at the step 1014 where theSU issues a write replicated slice request to an alternate SU. Forexample, the SU generates the request to include a correspondingalternate slice name and the replicated slice and outputs the request tothe alternate SU for storage therein.

For each of the one or more replicated slices, the method 1000 continuesat the step 1016 where the SU updates an index to associate acorresponding alternate slice name with a common data identifier. Forexample, the SU updates an index entry of the index associated with thedata identifier to include the corresponding alternate slice name and/oran alternate source name. The method 1000 continues at the step 1018where a processing module of a requesting entity (e.g., a computingdevice, a SU, a SU, and/or other device) obtains the common dataidentifier for data to retrieve (e.g., receive, look up). The method1000 continues at the step 1020 where the processing module of therequesting entity accesses the index utilizing the common dataidentifier to retrieve the index entry. The accessing includesperforming a lookup starting with a root node of the index based on thedata identifier or an attribute of the data and searching the index toidentify the index entry for retrieval. The method 1000 continues at thestep 1022 where the processing module of the requesting entity selects aset of slice names based on the index entry. The selecting may be basedon one or more of a priority indicator, a performance indicator, and arandom selection.

The method 1000 continues at the step 1024 where the processing moduleof the requesting entity issues at least a read threshold number of readslice requests using the selected set of slice names. The issuingincludes generating the requests using the selected set of slice namesand outputting the requests to the alternate SU and/or another alternateSU. The method 1000 continues at the step 1026 where the processingmodule of the requesting entity determines whether a threshold number ofslices have been received within a timeframe. The method 1000 branchesto the step 1030 where the processing module selects another set ofslice names when the threshold number of slices have not been receivedwithin the time frame. The method 1000 continues to the next step whenthe threshold number of slices have been received within the time frame.The method 1000 continues at the next step 1028 where the processingmodule of the requesting entity decodes receives slices to reproduce thedata. The method 1000 continues at the step 1030 where the processingmodule of the requesting entity further selects another set of slicenames based on the index entry. Further selecting further includesexcluding a previous slice name associated with failed responses. Themethod 1000 loops back to the step 1024 where the processing module ofthe requesting entity issues the at least the read threshold number ofread slice requests.

FIG. 11 is a diagram illustrating an embodiment of a method 1100 forexecution by one or more computing devices in accordance with thepresent invention. The method 1100 operates in step 1110 by obtaining adata identifier associated with a data object. In some examples, thedata object is segmented into a plurality of data segments, and a datasegment of the plurality of data segments is dispersed error encoded inaccordance with dispersed error encoding parameters to produce aplurality of encoded data slices (EDSs) that is distributedly storedamong a plurality of storage units (SUs) within a dispersed ordistributed storage network (DSN). Note that a read threshold number ofEDSs provides for reconstruction of the data segment.

The method 1100 then continues in step 1120 by determining one of moreDSN addresses associated with storage of one or more of the plurality ofEDSs. The method 1100 operates in step 1130 by selecting a plurality ofslice names based on the one of more DSN addresses. The method 1100 thencontinues in step 1140 by issuing (e.g., via an interface of thecomputing device that is configured to interface and communicate with adispersed or distributed storage network (DSN)) at least a readthreshold number of read slice requests using the plurality of slicenames to at least some of the plurality of SUs.

The method 1100 then operates in step 1150 by determining whether atleast the read threshold number of EDSs is received.

When the read threshold number of EDSs is received via the interfacefrom the at least some of the plurality of SUs in response to issuanceof the at least the read threshold number of read slice requests asdetermined in step 1160, the method 1100 then operates in step 1195 byreconstructing the data segment.

Alternatively, when fewer than the read threshold number of EDSs isreceived via the interface from the at least some of the plurality ofSUs in response to issuance of the at least the read threshold number ofread slice requests as determined in step 1160, the method 1100 thenoperates in step 1170 by issuing an alternate read slice request to analternate SU to retrieve an alternate EDS among the read thresholdnumber of EDSs. The method 1100 then operates in step 1150 bydetermining whether at least the read threshold number of EDSs isreceived including the alternate EDS.

When the read threshold number of EDSs received including the alternateEDS is received via the interface as determined in step 1190, the method1100 then operates in step 1195 by reconstructing the data segment.Alternatively, when the read threshold number of EDSs received includingthe alternate EDS is received via the interface as determined in step1190, the method 1100 then operates in step 1195 by reconstructing thedata segment.

Alternatively, when the alternate EDS among the read threshold number ofEDSs is not received via the interface from the alternate SU and thecomputing device has received at least the read threshold number ofEDSs, the method 1100 branches back to step 1170.

This disclosure presents, among other things, various novel solutionsthat provide for retrieval of data from a dispersed data storage system.For example, when requests for an object, segments of an object, and/orslices become too frequent for the SUs holding those slices to handle,then a temporary replica of those slices, segments, and/or object may bestored to a newly chosen location in the namespace in that vault. Havingan alternate namespace location requires having a different name, thusthe replicated slices (or segments) obtain aliases. The aliases for agiven slice name or source name can then be stored in a dispersed datastructure, such as a dispersed index or map. When a reader (e.g., acomputing device that make a read request to a SU) determines a requestfor a slice or segment, and/or object fails due to being overloaded, itperforms a look up in the dispersed index for the slice name, or sourcename(s) for the segment or object. The value associated with this lookupis a list of all the alternate slice names/source names, and the readermay choose any of them to satisfy the request. If the request fails, itthen uses another alias, and continues until every alternate name hasattempted and failed, or until one has succeeded.

It is noted that terminologies as may be used herein such as bit stream,stream, signal sequence, etc. (or their equivalents) have been usedinterchangeably to describe digital information whose contentcorresponds to any of a number of desired types (e.g., data, video,speech, audio, etc. any of which may generally be referred to as‘data’).

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “configured to”, “operably coupled to”, “coupled to”, and/or“coupling” includes direct coupling between items and/or indirectcoupling between items via an intervening item (e.g., an item includes,but is not limited to, a component, an element, a circuit, and/or amodule) where, for an example of indirect coupling, the intervening itemdoes not modify the information of a signal but may adjust its currentlevel, voltage level, and/or power level. As may further be used herein,inferred coupling (i.e., where one element is coupled to another elementby inference) includes direct and indirect coupling between two items inthe same manner as “coupled to”. As may even further be used herein, theterm “configured to”, “operable to”, “coupled to”, or “operably coupledto” indicates that an item includes one or more of power connections,input(s), output(s), etc., to perform, when activated, one or more itscorresponding functions and may further include inferred coupling to oneor more other items. As may still further be used herein, the term“associated with”, includes direct and/or indirect coupling of separateitems and/or one item being embedded within another item.

As may be used herein, the term “compares favorably”, indicates that acomparison between two or more items, signals, etc., provides a desiredrelationship. For example, when the desired relationship is that signal1 has a greater magnitude than signal 2, a favorable comparison may beachieved when the magnitude of signal 1 is greater than that of signal 2or when the magnitude of signal 2 is less than that of signal 1. As maybe used herein, the term “compares unfavorably”, indicates that acomparison between two or more items, signals, etc., fails to providethe desired relationship.

As may also be used herein, the terms “processing module”, “processingcircuit”, “processor”, and/or “processing unit” may be a singleprocessing device or a plurality of processing devices. Such aprocessing device may be a microprocessor, micro-controller, digitalsignal processor, microcomputer, central processing unit, fieldprogrammable gate array, programmable logic device, state machine, logiccircuitry, analog circuitry, digital circuitry, and/or any device thatmanipulates signals (analog and/or digital) based on hard coding of thecircuitry and/or operational instructions. The processing module,module, processing circuit, and/or processing unit may be, or furtherinclude, memory and/or an integrated memory element, which may be asingle memory device, a plurality of memory devices, and/or embeddedcircuitry of another processing module, module, processing circuit,and/or processing unit. Such a memory device may be a read-only memory,random access memory, volatile memory, non-volatile memory, staticmemory, dynamic memory, flash memory, cache memory, and/or any devicethat stores digital information. Note that if the processing module,module, processing circuit, and/or processing unit includes more thanone processing device, the processing devices may be centrally located(e.g., directly coupled together via a wired and/or wireless busstructure) or may be distributedly located (e.g., cloud computing viaindirect coupling via a local area network and/or a wide area network).Further note that if the processing module, module, processing circuit,and/or processing unit implements one or more of its functions via astate machine, analog circuitry, digital circuitry, and/or logiccircuitry, the memory and/or memory element storing the correspondingoperational instructions may be embedded within, or external to, thecircuitry comprising the state machine, analog circuitry, digitalcircuitry, and/or logic circuitry. Still further note that, the memoryelement may store, and the processing module, module, processingcircuit, and/or processing unit executes, hard coded and/or operationalinstructions corresponding to at least some of the steps and/orfunctions illustrated in one or more of the figures. Such a memorydevice or memory element can be included in an article of manufacture.

One or more embodiments have been described above with the aid of methodsteps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claims. Further, the boundariesof these functional building blocks have been arbitrarily defined forconvenience of description. Alternate boundaries could be defined aslong as the certain significant functions are appropriately performed.Similarly, flow diagram blocks may also have been arbitrarily definedherein to illustrate certain significant functionality.

To the extent used, the flow diagram block boundaries and sequence couldhave been defined otherwise and still perform the certain significantfunctionality. Such alternate definitions of both functional buildingblocks and flow diagram blocks and sequences are thus within the scopeand spirit of the claims. One of average skill in the art will alsorecognize that the functional building blocks, and other illustrativeblocks, modules and components herein, can be implemented as illustratedor by discrete components, application specific integrated circuits,processors executing appropriate software and the like or anycombination thereof.

In addition, a flow diagram may include a “start” and/or “continue”indication. The “start” and “continue” indications reflect that thesteps presented can optionally be incorporated in or otherwise used inconjunction with other routines. In this context, “start” indicates thebeginning of the first step presented and may be preceded by otheractivities not specifically shown. Further, the “continue” indicationreflects that the steps presented may be performed multiple times and/ormay be succeeded by other activities not specifically shown. Further,while a flow diagram indicates a particular ordering of steps, otherorderings are likewise possible provided that the principles ofcausality are maintained.

The one or more embodiments are used herein to illustrate one or moreaspects, one or more features, one or more concepts, and/or one or moreexamples. A physical embodiment of an apparatus, an article ofmanufacture, a machine, and/or of a process may include one or more ofthe aspects, features, concepts, examples, etc. described with referenceto one or more of the embodiments discussed herein. Further, from figureto figure, the embodiments may incorporate the same or similarly namedfunctions, steps, modules, etc. that may use the same or differentreference numbers and, as such, the functions, steps, modules, etc. maybe the same or similar functions, steps, modules, etc. or differentones.

Unless specifically stated to the contra, signals to, from, and/orbetween elements in a figure of any of the figures presented herein maybe analog or digital, continuous time or discrete time, and single-endedor differential. For instance, if a signal path is shown as asingle-ended path, it also represents a differential signal path.Similarly, if a signal path is shown as a differential path, it alsorepresents a single-ended signal path. While one or more particulararchitectures are described herein, other architectures can likewise beimplemented that use one or more data buses not expressly shown, directconnectivity between elements, and/or indirect coupling between otherelements as recognized by one of average skill in the art.

The term “module” is used in the description of one or more of theembodiments. A module implements one or more functions via a device suchas a processor or other processing device or other hardware that mayinclude or operate in association with a memory that stores operationalinstructions. A module may operate independently and/or in conjunctionwith software and/or firmware. As also used herein, a module may containone or more sub-modules, each of which may be one or more modules.

As may further be used herein, a computer readable memory includes oneor more memory elements. A memory element may be a separate memorydevice, multiple memory devices, or a set of memory locations within amemory device. Such a memory device may be a read-only memory, randomaccess memory, volatile memory, non-volatile memory, static memory,dynamic memory, flash memory, cache memory, and/or any device thatstores digital information. The memory device may be in a form a solidstate memory, a hard drive memory, cloud memory, thumb drive, servermemory, computing device memory, and/or other physical medium forstoring digital information.

While particular combinations of various functions and features of theone or more embodiments have been expressly described herein, othercombinations of these features and functions are likewise possible. Thepresent disclosure is not limited by the particular examples disclosedherein and expressly incorporates these other combinations.

What is claimed is:
 1. A computing device comprising: an interfaceconfigured to interface and communicate with a dispersed or distributedstorage network (DSN); memory that stores operational instructions; andprocessing circuitry operably coupled to the interface and to thememory, wherein the processing circuitry is configured to execute theoperational instructions to: obtain a data identifier associated with adata object, wherein the data object is segmented into a plurality ofdata segments, wherein a data segment of the plurality of data segmentsis dispersed error encoded in accordance with dispersed error encodingparameters to produce a plurality of encoded data slices (EDSs) that isdistributedly stored among a plurality of storage units (SUs) within theDSN, wherein a read threshold number of EDSs provides for reconstructionof the data segment; determine one of more DSN addresses associated withstorage of one or more of the plurality of EDSs; select a plurality ofslice names based on the one of more DSN addresses; issue at least aread threshold number of read slice requests using the plurality ofslice names to at least some of the plurality of SUs; when fewer thanthe read threshold number of EDSs is received from the at least some ofthe plurality of SUs in response to issuance of the at least the readthreshold number of read slice requests, issue an alternate read slicerequest to an alternate SU to retrieve an alternate EDS among the readthreshold number of EDSs; and when the alternate EDS among the readthreshold number of EDSs is received from the alternate SU and thecomputing device has received at least the read threshold number ofEDSs, reconstruct the data segment.
 2. The computing device of claim 1,wherein: a DSN address of the one of more DSN addresses includes atleast one of a slice name of the plurality of slice names, an alternateslice name, a source name, or an alternate source name; and the slicename and the source name are aliased to a common slice listed in anindex that associates the data identifier to the one of more DSNaddresses.
 3. The computing device of claim 1, wherein the processingcircuitry is further configured to execute the operational instructionsto: when the at least the read threshold number of EDSs is received fromthe at least some of the plurality of SUs in response to the issuance ofthe at least the read threshold number of read slice requests,reconstruct the data segment.
 4. The computing device of claim 1,wherein: a SU of the at least some of the plurality of SUs is configuredto determine to provide one or more alternate EDSs including thealternate EDS to the alternate SU to be stored temporarily in thealternate SU when the SU of the at least some of the plurality of SUs isoverloaded based on servicing requests for at least one EDS storedwithin the SU of the at least some of the plurality of SUs; and thealternate EDS to be stored temporarily in the alternate SU issubstantially same as an EDS stored within the SU of the at least someof the plurality of SUs.
 5. The computing device of claim 4, wherein theSU of the at least some of the plurality of SUs is further configured toissue a write replicated slice request to the alternate SU, wherein thewrite replicated slice request includes at least one of an alternateslice name, a replicated EDS, a storage time frame, or a performancethreshold.
 6. The computing device of claim 1, wherein the computingdevice is located at a first premises that is remotely located from asecond premises of at least one SU of the plurality of SUs within theDSN.
 7. The computing device of claim 1 further comprising: a SU of theplurality of SUs within the DSN, a wireless smart phone, a laptop, atablet, a personal computers (PC), a work station, or a video gamedevice.
 8. The computing device of claim 1, wherein the DSN includes atleast one of a wireless communication system, a wire lined communicationsystem, a non-public intranet system, a public internet system, a localarea network (LAN), or a wide area network (WAN).
 9. A computing devicecomprising: an interface configured to interface and communicate with adispersed or distributed storage network (DSN); memory that storesoperational instructions; and processing circuitry operably coupled tothe interface and to the memory, wherein the processing circuitry isconfigured to execute the operational instructions to: obtain a dataidentifier associated with a data object, wherein the data object issegmented into a plurality of data segments, wherein a data segment ofthe plurality of data segments is dispersed error encoded in accordancewith dispersed error encoding parameters to produce a plurality ofencoded data slices (EDSs) that is distributedly stored among aplurality of storage units (SUs) within the DSN, wherein a readthreshold number of EDSs provides for reconstruction of the datasegment; determine one of more DSN addresses associated with storage ofone or more of the plurality of EDSs, wherein a DSN address of the oneof more DSN addresses includes at least one of a slice name of aplurality of slice names, an alternate slice name, a source name, or analternate source name, and wherein the slice name and the source nameare aliased to a common slice listed in an index that associates thedata identifier to the one of more DSN addresses; select the pluralityof slice names based on the one of more DSN addresses; issue at least aread threshold number of read slice requests using the plurality ofslice names to at least some of the plurality of SUs; when the at leastthe read threshold number of EDSs is received from the at least some ofthe plurality of SUs in response to issuance of the at least the readthreshold number of read slice requests, reconstruct the data segment;when fewer than the read threshold number of EDSs is received from theat least some of the plurality of SUs in response to the issuance of theat least the read threshold number of read slice requests, issue analternate read slice request to an alternate SU to retrieve an alternateEDS among the read threshold number of EDSs; and when the alternate EDSamong the read threshold number of EDSs is received from the alternateSU and the computing device has received at least the read thresholdnumber of EDSs, reconstruct the data segment.
 10. The computing deviceof claim 9, wherein: a SU of the at least some of the plurality of SUsis configured to determine to provide one or more alternate EDSsincluding the alternate EDS to the alternate SU to be stored temporarilyin the alternate SU when the SU of the at least some of the plurality ofSUs is overloaded based on servicing requests for at least one EDSstored within the SU of the at least some of the plurality of SUs; andthe alternate EDS to be stored temporarily in the alternate SU issubstantially same as an EDS stored within the SU of the at least someof the plurality of SUs.
 11. The computing device of claim 10, whereinthe SU of the at least some of the plurality of SUs is furtherconfigured to issue a write replicated slice request to the alternateSU, wherein the write replicated slice request includes at least one ofan alternate slice name, a replicated EDS, a storage time frame, or aperformance threshold.
 12. The computing device of claim 9 furthercomprising: a SU of the plurality of SUs within the DSN, a wirelesssmart phone, a laptop, a tablet, a personal computers (PC), a workstation, or a video game device.
 13. The computing device of claim 9,wherein the DSN includes at least one of a wireless communicationsystem, a wire lined communication system, a non-public intranet system,a public internet system, a local area network (LAN), or a wide areanetwork (WAN).
 14. A method for execution by a computing device, themethod comprising: obtaining a data identifier associated with a dataobject, wherein the data object is segmented into a plurality of datasegments, wherein a data segment of the plurality of data segments isdispersed error encoded in accordance with dispersed error encodingparameters to produce a plurality of encoded data slices (EDSs) that isdistributedly stored among a plurality of storage units (SUs) within adispersed or distributed storage network (DSN), wherein a read thresholdnumber of EDSs provides for reconstruction of the data segment;determining one of more DSN addresses associated with storage of one ormore of the plurality of EDSs; selecting a plurality of slice namesbased on the one of more DSN addresses; issuing, via an interface of thecomputing device that is configured to interface and communicate with adispersed or distributed storage network (DSN), at least a readthreshold number of read slice requests using the plurality of slicenames to at least some of the plurality of SUs; when fewer than the readthreshold number of EDSs is received via the interface from the at leastsome of the plurality of SUs in response to issuance of the at least theread threshold number of read slice requests, issuing an alternate readslice request to an alternate SU to retrieve an alternate EDS among theread threshold number of EDSs; and when the alternate EDS among the readthreshold number of EDSs is received via the interface from thealternate SU and the computing device has received at least the readthreshold number of EDSs, reconstructing the data segment.
 15. Themethod of claim 14, wherein: a DSN address of the one of more DSNaddresses includes at least one of a slice name of the plurality ofslice names, an alternate slice name, a source name, or an alternatesource name; and the slice name and the source name are aliased to acommon slice listed in an index that associates the data identifier tothe one of more DSN addresses.
 16. The method of claim 14 furthercomprising: when the at least the read threshold number of EDSs isreceived from the at least some of the plurality of SUs in response tothe issuance of the at least the read threshold number of read slicerequests, reconstructing the data segment.
 17. The method of claim 14further comprising: operating a SU of the at least some of the pluralityof SUs to determine to provide one or more alternate EDSs including thealternate EDS to the alternate SU to be stored temporarily in thealternate SU when the SU of the at least some of the plurality of SUs isoverloaded based on servicing requests for at least one EDS storedwithin the SU of the at least some of the plurality of SUs; and storingthe alternate EDS temporarily in the alternate SU, wherein the alternateEDS is substantially same as an EDS stored within the SU of the at leastsome of the plurality of SUs.
 18. The method of claim 17 furthercomprising: operating the SU of the at least some of the plurality ofSUs to issue a write replicated slice request to the alternate SU,wherein the write replicated slice request includes at least one of analternate slice name, a replicated EDS, a storage time frame, or aperformance threshold.
 19. The method of claim 14, wherein the computingdevice includes a SU of the plurality of SUs within the DSN, a wirelesssmart phone, a laptop, a tablet, a personal computers (PC), a workstation, or a video game device.
 20. The method of claim 14, wherein theDSN includes at least one of a wireless communication system, a wirelined communication system, a non-public intranet system, a publicinternet system, a local area network (LAN), or a wide area network(WAN).